Vacuum Insulation Panel
A vacuum insulation panel has a non-porous insulating core with an upper surface and a lower surface and sides. An envelope is arranged about the core to envelop the core, and to maintain an applied vacuum within the envelope. A non-foam polyurethane coating layer is applied to the envelope. The coating layer is formed over the entire surface area of the envelope.
This application claims the benefit of U.S. Provisional Application No. 63/744,921, filed on January 14, 2025. The entire disclosure of the above application is incorporated herein by reference.
FIELDThe present invention relates to vacuum insulation panels (VIPs) and methods of manufacture thereof.
BACKGROUNDVIPs are used in many insulation applications including in insulation of buildings and in other applications such as refrigeration units and the like. Such panels generally have a panel of insulation material which forms an insulation “core” which is enveloped or wrapped in an envelope. The envelope is evacuated and sealed to provide a vacuum insulation panel.
The core is formed of any suitable material. For example the core may be formed from glass fibres.
Opacifiers, such as infra-red opacifiers can be used within the core.
The core is typically wrapped in a flexible, gas-tight envelope to which a vacuum is applied before sealing.
Thermal conductivity properties of VIPs typically range from 0.005W/(m·K) to 0.002 W/(m·K).
All thermal conductivities values referenced herein are those determined under BS EN: 12667:2001 unless expressly indicated otherwise. All thermal conductivity values expressed herein are measured in Watts (or milliwatts) per meter Kelvin.
When referring to the present invention, the term microns is the SI unit micrometres.
Notwithstanding the various VIP products that are available it is desirable to provide an alternative construction of VIP; an alternative method of making a VIP and/or a VIP with improved properties.
Some of the considerations that are taken into account when constructing a VIP are ease of manufacture, robustness of handling, availability and cost of materials, initial thermal conductivity value, and aged thermal conductivity value.
In relation to thermal conductivity there are many factors including the conductivity of the core and the conductivity of the envelope which influence the overall thermal conductivity of a VIP. The thermal conductivity of the core and of the envelope in turn depend on many other factors.
EP2607073 describes a VIP comprising a composite core material formed of glass fiber wool and glass fiber board and an outer skin material having a layered structure comprising a surface protective layer, a metal barrier layer, and a bonding layer from the outside to vacuum-package the core material. The object of EP2607073 is to provide a VIP which exhibits a long-term durability of 10 years or more. However, despite starting from an initial thermal conductivity of approximately 2.4 mW/(m·K), the predicted thermal conductivity after 2 years was approximately 6.4 mW/(m·K). By incorporating a glass fiber board, although the initial thermal conductivity is satisfactory, the lifetime of the board decreases rapidly over time. Notwithstanding the state of the art, there remains a long felt, yet unmet need to provide VIPs with improved thermal conductivity and a long-term durable lifetime. It is known that the thermal conductivity of a VIP product may be improved by reducing the density of the core, which has the added benefit of reducing the production cost of the VIP. However, a reduced density core is less robust and more prone to breakage and thus is more difficult to handle during the various production stages.
Thus, while it is desirable to reduce the density of the core as much as possible in order to improve thermal performance, the more the density is reduced, the more compromised are the handling properties of the core and any VIP made from it.
For example, conventional VIPs made from powder insulation silica cores with core density values of lower than about 165 kg/m3 have poor dimensional stability, the edges of the panels collapse and the panel envelope wrinkles. The result is an inferior product, which tends to warp over time and has an aesthetically displeasing appearance. A balance must therefore be struck between thermal performance and dimensional integrity on the one hand and ease of handling, on the other hand. Once the VIP has been made, it cannot be cut, so dimensional stability of the finished product is crucial.
One of the main problems for improving the longevity of VIPs is ingress of moisture and/or air through the envelope over time. One solution to the problem has been to increase the thickness of envelopes surrounding the core. While increasing the thickness of an envelope reduces its permeability to ingress of moisture and/or air, conduction through the envelope, in particular about the sides of the VIP is increased. Thermal bridging at the edges of a VIP decreases the insulating efficacy of the VIP because the envelope will have greater thermal conductivity than the core.
Improving the thermal performance of the core, improving the permeability of the envelope and reducing thermal bridging effects, is desirable, however, improvement of one property can often have a deleterious effect on other properties. Improving the thermal performance of VIPs and increasing their longevity, will augment their functionality, and increase their suitability for wider application.
SUMMARYIn one aspect, the present invention provides a vacuum insulation panel comprising:
(a) a non-porous insulating core having an upper surface and a lower surface and sides;
(b) an envelope about the core arranged to envelop the core, and to maintain an applied vacuum within the envelope; and
(c) a non-foam polyurethane coating layer applied to the envelope, wherein the coating layer is formed over the entire (external) surface area of the envelope.
Advantageously, the presence of the coating layer applied to the entire exterior of the envelope provides the envelope with a waterproof barrier. The coating is continuous over the entire surface of the envelope. Thus there are no discontinuities, such as voids or gaps in the coating. The coating also reduces susceptibility of the vacuum insulation panel to damage, in storage, in transit, during installation and throughout the lifetime of the panel. This results in enhanced vacuum retention and increases the longevity of the envelope and thus the VIP itself.
Suitably, the envelope comprises a metallised film, preferably, the envelope comprises a plurality of metallised films, for example, the envelope may comprise 3 or more metallised films bonded together to form a laminate. Advantageously, envelopes comprising metallised films have reduced thermal edge effects (thermal bridging at the edges past the core) in comparison to traditional aluminium envelopes.
Suitably, the polyurethane coating layer is less than about 5 mm thick. This advantageously ensures that the thickness of the VIPs is not significantly increased, thereby maintaining their utility in applications such as in refrigerators, while concomitantly increasing their longevity.
The coating layer may be at least about 0.05 mm thick, for example from about 0.1 mm to about 3 mm thick, such as from about 0.1 mm to about 1.5 mm thick.
Suitably, the coating layer is formed from a resin composition. The resin composition may be a two-part composition comprising a first isocyanate containing part and a second polyol containing part. Suitably the polyol containing part comprises at least one polyester polyol.
Suitably the polyurethane coating layer has a thickness of from about 0.1 mm to about 3 mm, and has a vapour resistance of from about 10 MN·s/g to about 100 MN·s/g, for example the polyurethane coating layer may have a vapour resistance of about 14 MN·s/g or more for a coating thickness of about 0.5 mm to about 3 mm. Suitably, the polyurethane coating layer may have a vapour resistance of 70 to 100 MN·s/g, such as about 70 MN·s/g or about 80 MN·s/g or about 90 MN·s/g, for a polyurethane coating layer having a thickness of from about 0.5 mm to about 3 mm.
The polyurethane coating layer may have a vapour resistivity of 5000 MN s/gm to about 100,000 MN·s/gm, suitably the polyurethane coating layer has a vapour resistivity of about 7000 MN·s/gm or more. For example the vapour resistivity may be about 6000 MN·s/gm to 10000 MN·s/gm, or about 10,000 MN·s/gm to 100,000 MN·s/gm, or about 20,000 MN·s/gm to 90,000 MN·s/gm, or about 30,000 MN·s/gm to 80,000 MN·s/gm or about 40,000 MN·s/gm to 70,000 MN·s/gm. Advantageously, the polyurethane coating increases the robustness of the vacuum insulation panel, by acting as a waterproof coating about the entire surface of the envelope of the vacuum insulation panel. This reduces the panel’s susceptibility to permeation from moisture, for example, rainwater in transit, or condensation when in storage or in use, and also provides a barrier to corrosive substances such as corrosive acid, which may for example leach from other insulation materials such as foams in close proximity to the vacuum insulation panel.
The polyurethane coating layer may be formed from a polyurethane resin composition. The composition may be applied in any suitable manner, such as by coating, for example by dip coating, curtain coating, by brushing or spraying the entire vacuum insulation panel with a suitable polyurethane resin composition.
The polyurethane resin composition may be a two-part composition comprising a first isocyanate containing part and a second polyol containing part. The isocyanate containing part may have a viscosity of from about 2000 mPa·s to about 3000 mPa·s when measured at 20 °C. The polyol containing part may have a viscosity of from about 2000 mPa·s to about 3000 mPa·s when measured at 20 °C. Suitably, the isocyanate containing part and the polyol containing part each have a viscosity of 2000 to 2500 mPa·s when measured at 20 °C, such as about 2300 mPa·s when measured at 20 °C. This facilitates easy application of the resin to the VIP envelope.
Suitably, the resin cures quickly, once applied to outer surface of the envelope, to provide a waterproof coating layer about the envelope.
The resin should be compatible with the barrier envelope and not result in corrosion of the barrier envelope.
The envelope and the polyurethane coating layer together form a barrier layer about the insulating core of the vacuum insulation panel. The barrier layer may have a moisture vapour transmission rate (MVTR) of from about 1.5 x 10-3 g/m2.day to about 3.0 x 10-3 g/m2.day, preferably about 2.5 x 10-3 g/m2.day or less, when measured in accordance with ASTM F1249-90. The barrier layer may have an oxygen transmission rate (OTR) of from about 2 x 10-3 cc/m2.day to about 5 x 10-3 cc/m2.day, preferably about 4 x 10 -3 cc/m2.day or less, when measured in accordance with ASTM D3985. Preferably, the MVTR is less than 2.5 x 10-3 g/m2.day and the OTR is less than 4 x 10-3 cc/m2day.
Advantageously, the presence of the polyurethane layer significantly increases the robustness of the vacuum insulation panel. This ensures that from the time of manufacture to the time of installation and throughout their lifetime, vacuum insulation panels according to the present invention are less likely to be accidentally perforated and permeation of moisture and air into the envelope is significantly reduced.
The envelope and the coating layer together form a barrier layer about the insulating core of the vacuum insulation panel. The barrier layer may have a moisture vapour transmission rate (MVTR) of from about 1.5 x 10-3 g/m2.day to about 3.0 x 10-3 g/m2.day, preferably about 2.5 x 10-3 g/m2.day or less, when measured in accordance with ASTM F1249-90. The barrier layer may have an oxygen transmission rate (OTR) of from about 2 x 10-3 cc/m2.day to about 5 x 10-3 cc/m2.day, preferably about 4 x 10-3 cc/m2.day or less, when measured in accordance with ASTM D3985. Preferably, the MVTR is less than 2.5 x 10-3 g/m2.day and the OTR is less than 4 x 10-3 cc/m2day.
Advantageously, the presence of the coating layer significantly increases the robustness of the vacuum insulation panel. When tested according to Fed-Std-101C, Method 2031, the puncture strenth of a VIP of the invention with a 1.5 mm layer of the polyurethane coating may be greater than about 750 N, for example greater than about 1000 N, for example greater than about 1200 N. For comparison, an equivalent VIP without the coating may achieve a puncture strength of less than 300 N.
A VIP of the present invention may achieve a compressive strength at 10% strain of greater than about 60 kPa, for example greater than about 70 kPa, for example greater than about 80 kPa when tested according to ASTM C165.
This ensures that from the time of manufacture to the time of installation and throughout their lifetime, vacuum insulation panels according to the present invention are less likely to be accidentally perforated and permeation of moisture and air into the envelope is significantly reduced.
The insulating core may be constructed from an insulating material comprising glass fibres, further details of which are provided below.
The insulating cores utilised in conventional VIPs, such as those constructed from a material comprising powdered insulating material, for example fumed silica have core densities in the range of from about 170 to about 200 kg/m3. The resulting thermal conductivity of conventional VIPs ranges from about 4.0 mW/(m·K) to about 5.0 mW/(m·K).
The insulating core may comprise glass, such as glass fibre and said insulating core may have a density of from about 120 kg/m3 to about 200 kg/m3. Optionally said insulating core may have a density of from about 140 kg/m3 to about 180 kg/m3.
The insulating core may comprise glass fibres, for example flame blown glass fibres, rotary (centrifugal spinneret blown) glass fibres, drawn glass fibres, or any combination thereof.
The insulating core may comprise glass fibres having an average nominal diameter of from about 0.1 microns to about 16 microns, for example from about 0.1 to about 5 microns, or about 3 micron to about 10 micron, or 8 micron to about 16 micron, when measured according to SEM analysis.
The insulating core may comprise glass fibres having an average length of from about 20 microns to about 25 mm, for example from about 20 to about 100 microns, or 3 mm to 25 mm, when measured according to SEM analysis or visual methods.
The insulating core may comprise glass fibres which have been formed into a fibrous mat. The glass fibres may have been formed into a fibrous may by a wet-laid process. Alternatively the glass fibres may have been formed into a fibrous mat by a dry-laid process.
The insulating core may have a pore size of from about 15 µm to about 20 µm, for example from about 16 µm to about 18 µm, when measured by means of a membrane bubble test (ASTM F316).
Vacuum insulation panels disclosed herein may comprise at least one metal foil having a thickness of from 4 microns to 50 microns, between the envelope and the insulating core and extending across substantially the entire surface of the insulating core on the upper surface or lower surface thereof and wherein the foil does not form a thermal bridge between the upper surface and lower surface of the insulating core. Suitably, the metal foil is attached to the inside of the envelope.
The envelope may comprise an envelope inner layer and the metal foil may have at least one outer layer attached thereto and the envelope inner layer and the outer layer on the metal foil may be attached to each other being optionally bonded to each other.
The vacuum insulation panels disclosed herein may comprise two metal foils having a thickness of from 4 micron to 50 micron wherein one metal foil extends across substantially the entire upper surface of the insulating core and a second metal foil extends across substantially the entire lower surface of the insulating core. Such a configuration is particularly suited to vacuum insulation panels for use in refrigerator panels, wherein a barrier to permeation for both major surfaces of the vacuum insulation panel is particularly advantageous.
The metal foil disposed between the insulating core and the envelope improves the permeation rate through the envelope. This means that air (gas) ingress into the envelope over time is reduced considerably with consequent improvement in the aged thermal conductivity of the VIP. The applied vacuum is maintained over a longer period of time. Maintenance of the vacuum over time means that the performance of the VIP from a thermal conductivity point of view is maintained for a longer period. This means that the useful lifetime of the VIP is improved.
The presence of metal foil advantageously facilitates a decrease in core density and a decrease in permeation through the envelope thereby enhancing the overall thermal insulation performance of the VIPs of the present invention.
In particular the present invention provides an envelope for the core which has improved permeation properties. In this context improved permeation is in fact reduced permeation because the lower the permeation the better, from the standpoint of maintaining a vacuum within the envelope. Reduced permeation of air (gas) into (through) the envelope over time results in an improved VIP performance.
The metal foil having a thickness of from 4 microns to 50 microns, such as from about 8 to 16 microns, will have a greater thermal conductivity than materials typically used for constructing a VIP envelope. For that reason it is important that a vacuum insulation panel of the invention will be constructed so that there is no thermal bridge formed by the metal foil that allows heat to be conducted past the core by bypassing the insulating core. If the metal foil were to extend beyond the upper surface (about the sides of the panel) and towards the lower surface (or vice versa) then the possibility of forming a thermal bridge increases with the consequent loss in performance in terms of thermal conductivity. From an insulation standpoint the lower the thermal conductivity of the panel the better. Thus whether the metal foil is present in the VIP across a major core surface or as a metal foil facer on a reinforcing member, in neither embodiment will the metal foil form a thermal bridge across the insulating core, i.e. from one major surface of the insulating core to the diametrically opposed other major surface of the insulating core.
The insulating core may have a parallelepiped or cuboid shape, comprising an upper surface, a lower surface and sides. The upper and lower surfaces (i.e. the major surfaces) are of larger surface area than the sides. The upper and lower surfaces are diametrically opposed surfaces. The metal foil is in direct contact with the core. The core may be encased in an air permeable cover or sleeve and the skilled person will appreciate that in such a case the metal foil is in direct contact with the sleeve encasing the core. The metal foil is not sandwiched between layers of the envelope. Specifically, the metal foil is not sandwiched between layers of the envelope, which form a thermal bridge about the core.
The metal foil layer has an inner surface and an outer surface. As outlined above, the metal foil is disposed between the inner surface of the envelope and the core, for example between the envelope and an upper (or lower) surface of the core. The metal foil itself has an inner surface and an outer surface, and the inner surface of the metal foil is proximate the core, while the outer surface of the metal foil is proximate the inner surface of the envelope.
The metal foil does not form a thermal bridge between the upper and lower surfaces. In particular there will be no thermal bridge formed by the metal foil. For example, the metal foil will not extend about the sides of the insulating core. Instead, the metal foil will be located only on the upper and/or lower surface of the insulating core. It will not bridge across the insulating core.
This means that any diminution in the overall thermal conductivity performance of the vacuum insulation panel which results from using the metal foil is not further compromised by a thermal edge effect with heat transfer through a thermal bridge which bypasses the core.
The present inventors have thus discovered that it is possible to have a construction where the overall aged thermal performance of the vacuum insulation panel is improved despite the use of metal foil(s) which have inferior thermal insulation performance, in comparison to the insulating core or the envelope, since the metal foil will be a far better thermal conductor than the insulating core or the envelope.
In particular, the inventors have discovered that it is possible to reduce air (gas) permeation through the envelope to an extent that it improves aged thermal performance, despite the use of a metal foil with a thermal conductivity that would typically be deemed unsuitable for use in VIPs as higher conductivity materials are traditionally considered to diminish thermal insulation performance.
This reduction in air (gas) permeation and resultant improvement in aged thermal insulation performance is accomplished by having an envelope that surrounds the core and having a metal foil that is only present on the upper and/or lower surface of the core.
The metal foil is attached to the inside of the envelope. Typically this is done after the vacuum is applied. The metal foil may be bonded to the inside of the envelope after a vacuum has been applied and after the VIP is formed. This may be achieved for example by heating the entire VIP in an oven. This step is conducted prior to coating the VIP with the coating.
In a vacuum insulation panel of the invention the envelope comprises an inner layer and the metal foil has at least one outer layer attached thereto wherein the envelope inner layer and the outer layer on the metal foil are attached to each other being optionally bonded to each other. In this context inner is with respect to the panel construction and in particular the core. So an inner layer on the envelope is on the side (e.g. of the envelope) that faces inwardly towards the core and an outer layer is on a side (e.g. of the metal foil) that faces outwardly away from the core.
As will be appreciated in order to minimise permeation, it would be desirable to have a permeation barrier across the entire envelope. It would be desirable that the permeation barrier surrounds the entire core.
In this respect VIPs that are already on the market have been constructed to be resistant to permeation. For example it is typical for a VIP to have an envelope constructed of a metallised film formed from a polymer film coated with one or more metallised layers. For example metallised PET (metallised polyethylene terephthalate) has been used to construct an envelope. Metallised films are constructed by applying a metal to a polymeric film, for example by applying the metal via a metal deposition technique on the desired film and the metallised layer of the metallised film is typically of the order of nanometres (in thickness). For example such a metallised layer may be of the order of 10 to 30 nm for example about 18 nm (thick). The metallised film (which comprises a polymer film coated with typically one or more metallised layers) is often of the order of 5 to 20 microns in thickness, for example about 12 microns in thickness. (This is the thickness of the polymer film and the metallised layer(s) taken together.) Often the metal used is aluminium.
As outlined above metallised film for example metallised PET can be used to create an envelope for a VIP. A metallised PET film, comprises a film of polyethylene terephthalate coated with at least one thin layer of metal (i.e. a metallised layer). To create a VIP a number of layers each layer being a metallised film, such as a PET metallised film of the type described above, can be used to create the envelope. In such cases the metallised film is formed as a laminate. The metallised layers may be attached to an inner envelope layer of for example polyethylene (PE). Other suitable inner envelope inner layers include low density polyethylene (LDPE) e.g. linear low density polyethylene (LLDPE), and ultra-high molecular weight polyethylene (UHMWPE); polypropylene and ethylenevinyl alcohol (EVOH), polyvinylidene chloride (PVDC); thermoplastic urethanes; including combinations thereof including copolymers and blends thereof.
In any event, the material forming the envelope is wrapped around the core and the envelope is then sealed to itself. This may be done by the application of heat around the edges of the envelope, for example by catching two edges of the envelope material between heating jaws and then applying pressure and heating to seal the material into an envelope. A vacuum is then applied and the position on the envelope where the vacuum is applied is finally sealed also to form a vacuum retaining envelope.
When an envelope is constructed in this way, by folding a material upon itself and heat sealing it about the edges to form the envelope, the same material is used throughout the envelope. In particular, in the case of an envelope constructed from one or more metallised layers, the metallised film extends across the entire inner surface of the envelope. In particular, it extends across the upper surface, across the lower surface, and across the sides and thus bridges between the upper and lower surfaces.
The metal foil layer used in vacuum insulation panels of the present invention can be used in conjunction with such an envelope construction. However, as mentioned above the metal foil layer of the present invention will not extend across the sides of the insulating core and will not bridge between the upper and lower surfaces of the core. Achieving such a construction according to the invention can be accomplished using the method of the invention as set out below.
In the arrangement described, the inner layer on the envelope and the outer surface of the metal foil are arranged proximate each other. The inner surface of the envelope and the metal foil may initially be provided separately and then later be joined. Typically the outer layer on the metal foil is provided across substantially the entire surface area of the upper and/or lower surface of the metal foil. As the metal foil corresponds substantially in surface area with the upper and/or lower surface of the core, this means that the metal foil is held on the inside of the envelope and in a position at which it aligns substantially with the upper and/or lower surface of the core. The metal foil does not extend from the upper and/or lower surface about the sides of the core.
Desirably the at least one metal foil is a rolled metal. The metal foil will be capable of being handled by itself. It is self-supporting and does not have to be provided on a support, albeit in some embodiments the metal foil may be provided as a facer on a reinforcing member. For convenience, and in particular for ease of attachment to the envelope, a layer may be provided on the metal foil, for example a layer may be provided at least on an outer surface thereof. That layer will be compatible with a layer of the envelope in order that the two layers may then be joined, for example by heating. Optionally, the layer provided on the outer surface of the metal foil is a polymer layer.
It will be appreciated that even though the material forming the envelope is edge sealed in order to form the envelope, this edge sealing will not join the metal foil to the envelope because the metal foil does not extend about the sides of the envelope. Instead the metal foil is attached to the envelope in a subsequent manufacturing step as will be described in more detail below.
The metal foil may be formed of a suitable metal, including combinations such as alloys. Suitable metals include aluminium and steel for example stainless steel.
Desirably the thickness of the at least one metal foil is of from 4 micron to 50 micron, or of from 4 micron to 30 micron, or of from 4 micron to 20 micron, or of from 4 micron to 18 micron, or of from 4 micron to 16 micron, or of from 4 micron to 14 micron, or of from 4 micron to 12 micron, or of from 6 micron to 20 micron, or of from 6 micron to 18 micron, or of from 6 micron to 16 micron, or of from 6 micron to 14 micron, or of from 6 micron to 12 micron, or of from 8 micron to 20 micron, or of from 8 micron to 18 micron, or of from 8 micron to 16 micron, or of from 8 micron to 14 micron, or of from 8 micron to 12 micron.
Within the invention the at least one metal foil may be rolled aluminium for example rolled aluminium having a thickness of about 12 micron.
Desirably a vacuum insulation panel of the invention comprises two metal foils, wherein one metal foil extends across substantially the entire surface of the core on the upper surface and a second metal foil extends across substantially the entire surface of the core on the lower surface.
Desirably a metal foil extends across at least 80%; such as at least 85%; for example at least 90% for example at least 95% of an upper or lower surface of the core.
Within the invention an inner layer of the envelope may comprise a thermoplastic material which softens sufficiently to be heat sealed. The softening occurs at a temperature lower than the temperature at which the integrity of the envelope is compromised.
The thermoplastic material may be selected from the group consisting of polyethylene including low density polyethylene (LDPE) e.g. linear low density polyethylene (LLDPE), and ultra-high molecular weight polyethylene (UHMWPE); polypropylene and ethylenevinyl alcohol (EVOH), polyvinylidene chloride (PVDC); thermoplastic urethanes; including combinations thereof including copolymers and blends thereof.
Any suitable grade of material may be utilised. These include plasticised grades, flame retardant grades and combinations thereof.
Where an outer layer is provided on the metal foil the outer layer may comprise a thermoplastic polymer selected from the group consisting of polyethylene, polypropylene and ethylenevinyl alcohol or copolymers thereof.
An outer layer is provided on the metal foil and an inner layer is provided on the envelope and the outer layer on the metal foil and the inner layer on the envelope are bonded by heating the panel.
It is desirable that the metal foil attaches across substantially its entire surface area to the inside of the envelope. For example, when attached, the envelope and the metal foil may effectively form a laminate structure. The metal forms the innermost layer of said laminate structure. The skilled person will appreciate that the metal foil is proximate the core. The metal foil is not sandwiched between layers of plastic which form a thermal bridge about the core.
The inner layer of the envelope may comprise a polyethylene material such as a polyethylene film and the outer layer on the metal foil may comprise a polyethylene material such as a polyethylene coating.
The inner layer of the envelope which attaches to the metal foil may have a thickness in the range from about 10 to about 50 microns. The outer layer of the metal foil which attaches to the envelope may have a thickness in the range from about 10 to about 50 microns.
As mentioned above, the metal foil may be attached to a layer, and said layer may be attached to the outer surface of the metal foil. The layer may be typically a polymer layer. The layer is a thermoplastic polymer layer. The layer is attached to the metal foil by any desired method including utilising adhesive. The layer attached to the metal foil, may for example be polyethylene (PE). In such a case, the metal foil may form part of a laminate structure. Whether in a laminate structure or not, the metal foil will not be directly (or indirectly) attached to the inner surface of the envelope until after the vacuum is applied. Optionally, a layer may also be attached to the inner surface of the metal foil. This layer is typically a polymer layer, optionally a thermoplastic polymer layer and said layer may be attached to the metal foil by any desired method including utilising adhesive. This inner layer on the metal foil does not extend about the sides of the core. For example, the metal foil inner layer does not form a thermal bridge between the upper surface of the core and the lower surface of the core. The inner layer may be substantially the same size as the metal foil, suitably, the inner layer on the metal foil is the same size as the metal foil.
Suitably, the envelope comprises a metallised film, for example the envelope may comprise a plurality of metallised films, for example, in a laminate structure. Optionally three metallised films may be provided within a laminate structure. In such an arrangement the metallised side of the film would typically face outwards (towards the exterior of the envelope).
A further layer may be provided as the inner layer of the envelope. Such a layer will typically be a non-metallised layer. As outlined above, the further layer may be a polyethylene layer. Again, the overall structure of the envelope may be provided as a laminate and the envelope is then created from that laminate. The envelope is sealed by edge sealing. However, the metal foil, or any laminate in which the metal foil is incorporated, is not attached to the envelope by the edge sealing process.
The material supporting the metal layers in the metallised film will typically be a polymeric material. It will be selected to have a higher melting point than the inner layer of the envelope. For example the envelope may be constructed of a plurality of layers of metallised PET whereas the inner layer of the envelope may be formed from PE.
Typically PET has a melting point that is greater than that of polyethylene. For example PET may have a melting point that is greater than 250°C. Polyethylene has a melting point typically in the range from about 105 to 180°C. For example low density polyethylene may have a melting point in the range from about 105 to 115°C. For example medium to high density polyethylene may have a melting point in the range from 115 to 180°C.
Typical metallised films have an oxygen transmission rate (OTR) of less than about 2 x 10-3 cc/m2day as measured according to ASTM D3985 (measured at 23 oC with 50% relative humidity) and moisture vapour transmission rates of about 0.02 g/m2day as measured according to ASTM F1249-90 (measured at 38 oC with 100% relative humidity). In contrast typical aluminium foils have an oxygen transmission rate of less than about 5 x 10-4 cc/m2day measured according to ASTM D3985 (measured at 23 oC with 50% relative humidity) and moisture vapour transmission rates of less than about 0.005 g/m2day as measured according to ASTM F1249-90 (measured at 38 oC with 100% relative humidity). The aforementioned values are measured for planar film samples and the planar film samples do not have seals such as those found in a VIP envelope.
In a VIP envelope, defects in the envelope barrier material and the presence of an envelope seal lead to a permeation value for the envelope which is higher than a permeation value determined for a planar film sample as utilised according to the above-mentioned standard test methods. The permeation through an envelope is thus generally higher due to permeation through the envelope seals, which do not possess a metallisation barrier. The overall oxygen transmission rate through a traditional VIP envelope is typically an order of magnitude higher than that for a planar film, due to the presence of the non-metallised seals; i.e. the oxygen transmission rate through a traditional metallised film VIP envelope is about 20 x 10-3 cc/m2day.
While the OTR for a VIP envelope made of metallised film (e.g. metallised PET) is about 20 x 10-3 cc/m2.day, the OTR for a VIP envelope made of aluminium foil is about 5 x 10-3 cc/m2.day.
As outlined above, the VIPs of the present invention have increased longevity owed to decreased OTR and MVTR. Furthermore, the presence of the coating layer on the outer surface of the envelope improves the vapour resistivity of the VIP.
In some embodiments, the vacuum insulation panels of the present invention may further comprise a layer of adhesive on the outer surface of the panel, for example on the outer surface of the coating layer. Suitably, the adhesive is a pressure sensitive adhesive layer. The layer of adhesive may have a release substrate attached thereto, which is removed prior to installation of the vacuum insulation panel. Advantageously, the presence of the layer of adhesive facilitates installation of the panel, enabling the user to adhere the panel to a substrate such as a wall, cladding or roof. Suitably, the pressure sensitive adhesive is not a hot melt adhesive.
Advantageously, the VIPs of the present invention can be incorporated into shipping containers, pipe insulation, refrigerators, coolers, and in a variety of industrial appliances. Furthermore, the VIPs of the present invention are lightweight, more robust than traditional VIPs and can be used in a variety of environments. For example, the VIPs of the present invention can be used in cryogenic apparatus and also at elevated temperature (up to 80 oC) without jeopardising their insulating performance.
The present invention also provides a process for manufacturing a vacuum insulation panel comprising the steps of:
(i) providing a non-porous insulating core having an upper surface and a lower surface and sides;
(ii) providing at least one metal foil having a thickness of at least 4 microns which extends across substantially the entire upper surface or entire lower surface of the core so that the foil does not form a thermal bridge between the upper surface and lower surface of the core;
(iii) providing an envelope having an inside surface and an outside surface, wherein the envelope is arranged to: (i) envelop the core and the metal foil, with the metal foil between the envelope and the core, and (ii) to maintain an applied vacuum within the envelope;
(iv) applying a vacuum to the envelope;
(v) attaching the metal foil to an inside surface of the envelope after the vacuum has been applied; and
(vi) coating the entire external surface of the vacuum insulation panel with a non-foam polyurethane layer.
By completing the attaching step after applying the vacuum, the pressure differential across the envelope (caused by reduced pressure within the envelope due to application of the vacuum) creates a very strong urging force for mating the metal foil to the inside of the envelope. In essence then atmospheric pressure is sufficiently strong to press the envelope against the metal foil and in turn the metal foil against the core. This pressure is sufficient to allow the two separate parts (the metal foil and the envelope) to be joined across their entire mating area.
It will be appreciated that the attaching step can be done after any equipment for applying the vacuum has been removed. That is the attaching step can be carried out when the retained vacuum within the envelope is the only vacuum present. So the attaching step can be done after the VIP has been evacuated and then sealed to retain the vacuum. It is the vacuum within the evacuated and then sealed envelope that is present.
The metal foil will be placed so as to reduce the permeability of the envelope across substantially the entire upper or lower surface area of the core.
Where the envelope comprises an envelope inner layer and the metal foil has at least one outer layer attached thereto the envelope inner layer and the outer layer on the metal foil are attached to each other and are optionally bonded to each other.
Any construction of vacuum insulation panel of the invention described herein may be made by the process of the invention.
The inner layer of the envelope may comprise a polymer selected from the group consisting of polyethylene, polypropylene and ethylenevinyl alcohol or copolymers thereof.
The outer layer on the metal foil may comprise a polymer selected from the group consisting of polyethylene, polypropylene and ethylenevinyl alcohol or copolymers thereof.
The metal foil and the inside surface of the envelope may be attached to each other by heating the panel (after the vacuum is applied). Suitably, the entire panel is heated in an oven. By heating the entire panel as opposed to simply heating the upper and or lower surface thereof, the edge seal is significantly enhanced.
The metal foil and the inside surface of the envelope may be attached to each other by heating the panel to a temperature of between about 100 and 180 degrees Celsius optionally for approximately 0.5 to 10 minutes.
After heating to a temperature in the range from about 100 and 180 degrees Celsius for approximately 0.5 to 10 minutes, the panel is cooled to ambient temperature within approximately 1 to 15 minutes.
A conventional VIP comprising an insulating core constructed from a microporous material has a thermal conductivity (lambda value) of approximately 5.0 mW/(m·K). In contrast VIPs of the present invention have a thermal conductivity of about 3.0 mW/(m·K) to about 4.0 mW/(m·K); desirably VIPs of the present invention have a thermal conductivity value of about 3.5 mW/(m·K) or less such as about 3.2 mW/(m·K) or less.
VIPs of the present invention have improved thermal conductivity values, and longer lifetime than traditional VIPs as permeation through the barrier envelope is reduced due to the presence of the at least one metal foil layer within the VIP and damage as a result of exposure to moisture is reduced by the presence of the non-foam polyurethane coating layer applied to the envelope. VIPs of the present invention are more robust than traditional VIPs and less susceptible to perforation as a consequence of the additional non-foam polyurethane coating layer.
Furthermore, the seal about the edges of envelope of VIPs of the present invention, is substantially stronger and larger than the seal about the edges of a traditional VIP, due to the method of manufacture of the present VIP, which is explained in detail below.
The insulating core may comprise glass, such as glass fibres.
The insulating core may have a density of from about 120 kg/m3 to about 200 kg/m3. Optionally said insulating core may have a density of from about 140 kg/m3 to about 180 kg/m3.
The insulating core may comprise glass fibres, for example flame blown glass fibres, rotary (centrifugal spinneret blown) glass fibres, drawn glass fibres, or any combination thereof.
The insulating core may comprise glass fibres having an average nominal diameter of from about 0.1 microns to about 16 microns, for example from about 0.1 to about 5 microns, or about 3 micron to about 10 micron, or 8 micron to about 16 micron, when measured according to SEM analysis.
The insulating core may comprise glass fibres having an average length of from about 20 microns to about 25 mm, for example from about 20 to about 100 microns, or 3 mm to 25 mm, when measured according to SEM analysis or visual methods.
The insulating core may comprise glass fibres which have been formed into a fibrous mat. The glass fibres may have been formed into a fibrous may by a wet-laid process. Alternatively the glass fibres may have been formed into a fibrous may by a dry-laid process.
The core may be encased in an air permeable cover or fleece prior to encasing the core and the at least one metal foil layer(s) in the flexible envelope.
For example, the air permeable cover may be selected from non-woven PET fleece or perforated shrink wrap.
The envelope may be constructed of metallised polyethylene terephthalate (PET) laminate. Suitably, the envelope is an aluminium metallised polyester comprising a layer of polyethylene on the aluminium, for example as a laminate. When forming the VIP the layer of polyethylene is within the envelope. The polyethylene layer is employed to seal the VIP once the envelope comprising the core and the at least one metal foil layer(s) is evacuated. The envelope may also be metallised ethylene vinyl alcohol (EVOH), or metallised polypropylene (PP).
Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings in which:
It will be noted that the foils 9a and 9b are not attached to the core 3. Instead they are initially separate from the envelope 2 and the core 3 and are later attached to the envelope 2 as will be described below.
The enlarged view of the metal foil structure 901 shows the metal foil 9a with an outer layer 12 attached thereto. The outer layer 12 is typically a thermoplastic polymeric material, for example polyethylene.
As shown in
The ability of a VIP envelope to maintain a defined vacuum during the lifetime of a VIP is of great importance in achieving and maintaining long-term thermal performance. Thermal edge effects occur due to the relatively high thermal conductivity of the envelope material which envelops the insulating core. Thermal edge effects are observed because the envelope acts as a thermal bridge around the insulating core, which has a very low thermal conductivity, once a vacuum is maintained, within the VIP.
Choosing a material suitable for a VIP envelope is therefore a balance between selecting a material with a desirably low thermal conductivity and a low permeation. Metallised films as described above which are employed as envelopes in traditional VIPs have a reasonably low thermal conductivity. However, their permeability substantially reduces the lifetime and therefore, overall utility of traditional VIPs.
The thermal conductivity of aluminium is 167 W/(m·K). Accordingly, aluminium is not a suitable material for a VIP envelope, due to the high edge effects which would be observed as a consequence of aluminium’s high thermal conductivity value. However, aluminium foils have excellent barrier properties.
VIPs of the present invention comprising a metal foil layer of from 4 microns to 50 microns, provide a significant advancement over prior art VIPs. Such VIPs marry the desirable low thermal conductivity properties of traditional VIP envelopes with the desirable low permeability properties of metal foils.
For the embodiments shown in the figures, after a vacuum is applied and the edge of the VIP is sealed, the metal foil disposed between the inner surface of the envelope and at least the upper surface of the insulating coreis attached to the inner surface of the envelope. For example, the metal foil may be attached to an outer layer of thermoplastic material, such as polyethylene and the envelope may have an inner envelope layer made of a thermoplastic material, such as polyethylene. As the VIP is evacuated the outer surface on the metal foil will be in close proximity to the inner surface of the envelope inner layer. When the VIP is heated, for example in an oven, to a temperature sufficiently high to soften the thermoplastic materials, the metal foil becomes attached to the inside surface of the envelope. The metal foil is arranged so as not to form a thermal bridge across the insulating core. However, the excellent low permeation properties of the foil significantly improve the permeation properties of the VIP. Accordingly, the lifetime of the VIP is significantly increased. It will be appreciated that the attachment of the foil to the envelope can be done after the VIP has been formed and in particular after any vacuum source has been removed. The vacuum retained within the envelope will assist in joining the foil to the envelope. Effectively the pressure differential between atmospheric pressure to the exterior of the VIP and the retained (reduced) pressure within the VIP imparts a force pressing the envelope towards the foil (and the core). And of course this force is imparted uniformly across the envelope. This is ideal for uniform joining of the envelope to the foil.
The procedural step of heating the evacuated VIP in an oven also improves the original heat seal at the edge of the envelope.
Because the envelope of a VIP is traditionally sealed between heating jaws as described above, only the area of the envelope directly exposed to the heat of the heating jaws is heated sufficiently in order to melt the thermoplastic inner envelope layer and join the two proximate edges. Edges of the envelope in close proximity which have not been exposed to elevated temperature are not joined/bonded.
In contrast, in the embodiment described above, whereby the metal foil of a VIP according to the present invention is attached to the inner surface of the VIP envelope, by heating the entire VIP (post evacuation), edges of the envelope which are proximate, which were not originally bonded by the heating jaws, remain proximate due to the external pressure applied to the evacuated VIP and when heated the thermoplastic layers of said edges soften and a bond is formed therebetween.
Thus while the presence of the metal foil attached to the envelope, provides an ultra-low permeation envelope, the seal of the VIPs of the present invention are considerably enhanced, in comparison to those of traditional VIPs, accordingly, the lifetime of the VIPs of the present invention are significantly longer than traditional VIPs without reducing the thermal performance.
The presence of the non-foam polyurethane coating substantially increases the robustness of the VIP. The polyurethane coating provides a protective coating on the outer surface of the VIP which provides the VIP with a waterproof coating, and also increases the barrier protection, making accidental perforation of the VIP less likely. Accordingly, the VIPs of the present invention, are less susceptible to damage, for example when stored on site, prior to installation.
Suitably, the non-foam polyurethane coating provides excellent wear resistance and long term durability to the VIP. For example, the polyurethane coating may in addition to providing waterproofing, also provide resistance to damage from UV rays or resistance to corrosive materials such as acidic materials. Suitably, the polyurethane coating is flexible and crack resistant.
The words “comprises/comprising” and the words “having/including” when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.
It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.
Claims
1. A vacuum insulation panel comprising:
- (a) a non-porous insulating core having an upper surface and a lower surface and sides;
- (b) an envelope about the core arranged to envelop the core, and to maintain an applied vacuum within the envelope; and
- (c) a non-foam polyurethane coating layer applied to the envelope, wherein the coating layer is formed over the entire surface area of the envelope.
2. A vacuum insulation panel according to claim 1, wherein the envelope comprises a metallised film.
3. A vacuum insulation panel according to claim 1, wherein the polyurethane coating layer is less than about 5 mm thick.
4. A vacuum insulation panel according to claim 1, wherein the polyurethane coating layer is from about 0.1 mm to about 3 mm thick, such as from about 0.1 mm to about 1.5 mm thick.
5. The vacuum insulation panel according to claim 1, wherein the polyurethane coating layer has a vapour resistivity of from 5000 MN·s/gm to 100000 MN·s/gm, preferably the polyurethane coating layer has a vapour resistivity of about 7000 MN·s/gm or more.
6. The vacuum insulation panel according to claim 1, wherein the polyurethane coating layer is formed from a polyurethane resin composition comprising a first isocyanate containing part and a second polyol containing part.
7. The vacuum insulation panel according to claim 1, wherein the envelope and the polyurethane coating layer form a barrier layer about the insulating core, said barrier layer having a moisture vapour transmission rate of from about 1.5 x 10-3 g/m2.day to about 3.0 x 10-3 g/m2.day, preferably about 2.5 x 10-3 g/m2.day or less, when measured in accordance with ASTM F1249-90.
8. A vacuum insulation panel according to claim 1, wherein the vacuum insulation panel achieves a puncture strength of greater than about 750 N, when tested according to Fed-Std-101C, Method 2031 with a 1.5mm thick layer of the coating.
9. A vacuum insulation panel according to claim 1, having a thermal conductivity of less than 4.0 mW/(m·K), for example of less than 3.5 mW/(m·K), for example of less than 3.0 mW/(m·K).
10. A vacuum insulation panel according to claim 1, wherein the insulating core comprises glass, such as glass fibres.
11. A vacuum insulation panel according to claim 1, wherein the insulating core comprises glass fibres having an average nominal diameter of from about 0.1 microns to about 16 microns, when measured according to SEM analysis.
12. A vacuum insulation panel according to claim 1, wherein the insulating core comprises glass fibres having an average length of from about 20 microns to about 25 mm, for example from about 20 to about 100 microns, or for example from 3 mm to 25 mm, when measured according to optical microscopy.
13. A vacuum insulation panel according to claim 1, wherein the insulating core comprises glass fibres which have been formed into a fibrous mat.
14. A process for manufacturing a vacuum insulation panel, comprising the steps of: (i) providing a non-porous insulating core having an upper surface and a lower surface and sides; (ii) providing at least one metal foil having a thickness of at least 4 microns which extends across substantially the entire upper surface or entire lower surface of the core so that the foil does not form a thermal bridge between the upper surface and lower surface of the core; (iii) providing an envelope having an inside surface and an outside surface, wherein the envelope is arranged to: (i) envelop the core and the metal foil, with the metal foil between the envelope and the core, and (ii) to maintain an applied vacuum within the envelope; (iv) applying a vacuum to the envelope; (v) attaching the metal foil to an inside surface of the envelope after the vacuum has been applied; and (vi) coating the entire external surface of the vacuum insulation panel with a non-foam polyurethane layer.
Type: Application
Filed: Jan 6, 2026
Publication Date: Jul 30, 2026
Inventors: Daniel MACK (Leominster), Bahadir ÖZSOYLU (Leominster), Samuel BUTLER (Leominster), Tony SCOTT (Leominster), Anthony HAYNES (Leominster), Ray VARONA (Atlanta, GA)
Application Number: 19/440,776
